A motor grader is used to rough or finish grade an earth surface and includes a base unit with a main frame supporting traction wheels, operator cab, engine compartment, transmission, and a belly mounted (moldboard) blade. The blade extends downwardly from a circle drive arrangement which adjusts the angular orientation of the blade relative to a generally vertical axis. The circle drive arrangement is movably connected with the main frame at the front end. A blade positioning linkage attached to the main frame interconnects with the rear of the circle drive arrangement via a pair of blade positioning cylinders.
When using a motor grader it is important to have as much visibility as possible to and around the front axle and tires, as well as the blade. A blade positioning linkage having deficiencies in visibility to and around the front axle and tires causes the operator to lean or adjust his position in the seat to gain the visibility needed to perform certain tasks. It is also important to see out over the main frame to be able to see objects in the machines path. Visibility is impaired with a blade positioning linkage that wraps completely around the main frame.
Conventional blade positioning linkages typically either use a 4-bar type linkage with sculpted arms to hold the blade positioning cylinders or use a single sculpted piece that is attached to and completely wraps around the main frame. Examples of blade positioning linkages are disclosed in U.S. Pat. No. 4,696,350 (Ruhter et al.) and U.S. Pat. No. 3,986,563 (Stubben), each of which are assigned to the assignee of the present invention.
What is needed in the art is a blade positioning assembly which allows movement of the blade relative to the main frame while at the same time providing increased visibility to the blade and front axle.